Field of the Invention
The present invention relates to a method for determining a mask pattern, a recording medium, and an information processing apparatus.
Description of the Related Art
In recent years, with the advance of miniaturization of semiconductor devices, it has been difficult to transfer a desired pattern onto a wafer with high accuracy by using an exposure apparatus. One cause of this may be a reduced half pitch that is the half of a shortest distance between patterns included in a circuit.
In order to address this problem, multiple-exposure patterning has been gathering attention as a technology for transferring a minute pattern such as 22 nm node onto a wafer with high accuracy. This technology is used to divide a pattern having a half pitch smaller than the half pitch of a resolution limit of an exposure apparatus into a plurality of mask patterns and expose them for transfer of a minute pattern with higher accuracy than in a case where the pattern is exposed once as in the past.
Multiple exposure patterning may require determination of a plurality of lithography-friendly mask patterns with which resolving performance such as a depth of focus may be improved and a yield may be improved. A method for determining such a plurality of mask patterns is disclosed in United States Patent Application Publication No. 2007/31740, Description, and United States Patent Application Publication No. 2010/223590, Description.
United States Patent Application Publication No. 2007/31740, Description, discloses a method in which a decomposition rule is applied to a pattern based on an iterative method. More specifically, the method includes determining first a pattern decomposition rule, determining whether a target pattern element belongs to a first mask or a second mask based on the rule, and repeating the operation for each pattern element. According to the decomposition rule, a pattern is decomposed in accordance with a result of determination on whether it is critical or not based on a line width of a pattern or a distance between patterns.
United States Patent Application Publication No. 2010/223590, Description, discloses a method for determining a plurality of mask patterns for performing exposure twice by assuming that two types of dipole illumination for a light intensity distribution (effective light source distribution) are formed on a pupil plane of an illumination optical system that illuminates a mask. More specifically, this method includes analyzing which illumination of x- and y-direction dipole illuminations is suitable for transferring a pattern to be decomposed and determining two types of mask pattern. A pattern having longitudinal edges extending in the y-direction is determined as a mask pattern for an x-direction dipole illumination while a pattern having longitudinal edges extending in the x-direction is determined as a mask pattern for a y-direction dipole illumination. In United States Patent Application Publication No. 2007/31740, Description, each mask pattern is determined in consideration of a line width of a pattern or a distance between patterns but not in consideration of angles between a plurality of pattern elements. This results in a plurality of pattern elements having different angles included in one mask. When the mask is illuminated by one effective light source distribution, the ease of resolution of the pattern elements may vary, and some pattern elements may have difficulty in being resolved.
According to United States Patent Application Publication No. 2010/223590, Description, mask patterns are divided by associating directions of edges of pattern elements and directions of dipole illuminations. However, relative positional relationships among a plurality of pattern elements, that is, the distances or angles between a plurality of pattern elements are not taken into consideration. This results in presence of a plurality of pattern elements having different relative positional relationships in one mask. When the mask is illuminated by one effective light source distribution, the ease of resolution of the pattern elements may vary, and some pattern elements may have difficulty in being resolved.